Lua for Elixir
68 comments
·May 13, 2025rickcarlino
benwilber0
> I am surprised more projects don’t provide a Lua scripting layer.
Completely agree. I've been adding Lua scripting support to pretty much everything I make now. Most recently my programmable SSE server [1]. It's extended the functionality far beyond anything that I would have had the time and patience to do myself. Lua is such a treat.
interroboink
This is not embedding the C Lua runtime and compiler, but rather a
complete implementation of Lua 5.3. This feat is made possible by the
underlying Luerl library, which implements a Lua parser, compiler,
and runtime, all in Erlang.
Also a sign of Lua's maturity and popularity, that it's got various independent implementations (LuaJIT, this one, perhaps others I don't know about).
johnisgood
LuaJIT is definitely amazing.
_acco
This is so cool. A key benefit is that it's not embedding the C Lua runtime and compiler, but rather implements Lua in the host language (Elixir/Erlang).
When sandboxing user code in another runtime, you need to serialize the data to and from that runtime. That comes with a performance penalty.
So, for example, if you sandbox code in WASM, you need to pick a transport data format, like JSON. You need to serialize Elixir data structures into JSON, send it to WASM, and then deserialize the result. For a high-performance data pipeline, this adds up!
But if your sandbox is in the host language, no serialization/de-serialization is required. You can execute the sandboxed language in microseconds.
I wrote more about this here: https://blog.sequinstream.com/why-we-built-mini-elixir/
Wish this library existed just a couple months ago!
Philpax
Very nice, but it is confusing to name a library for using a language the same thing as that language. I suppose this is meant to be a temporary state of affairs while Lua (the library) gets merged into Luerl, but I would have personally called it Luerl++ or such.
toast0
Within the BEAM ecosystem, consensus is to call something whatever2.
If you wait long enough before replacing whatever2 with something that would be whatever3, you can go back to whatever (see pg -> pg2 -> pg)
davydog187
Author here!
Luerl++ is not a valid module name :)
More seriously, I considered alternate names, but settled on this because it was short, literal, and given that its in the context of Elixir, makes sense when using it.
As you stated, the hope is to consolidate it into Luerl at some point
davydog187
If you're looking for a cool example of Lua running on the BEAM, check out the creator of Luerl (Robert Virding) space ship demo
pentacent_hq
I've been considering adding Lua support to Keila for a while already. It seems like a perfect fit for when I'm going to implement email automation and want to allow custom business logic. This would certainly make that plan easier. Thanks OP for sharing the library with the community!
davydog187
Let me know if you have any questions, I'd be happy to assist
gilgamesh3
Cool project, congrats.
I am trying to understand why would anyone prefer to use Lua to create script instead of Elixir, which supports running scripts. While Lua has lots of users the language just have too many wrong design choices. If I had the choice between Elixir and Lua for scripts I would use Elixir every time.
davydog187
Elixir is not a sandboxed language, so you can't just accept arbitrary Elixir programs from users and execute them inside of your application without security concerns. Lua, on the other hand, can be executed in a sandboxed fashion, limiting and constraining the reach of user programs.
Check out Anthony Accomazzo's post about Mini-Elixir, which does a great job breaking this down much further https://blog.sequinstream.com/why-we-built-mini-elixir/
prophesi
I would also personally prefer Elixir to Lua, but this would be great for allowing isolated/sandboxed BEAM processes to execute Lua code from your end users whom are likely unfamiliar with Elixir. As mentioned in the article, this is precisely what TV Labs uses it for to allow smart tv app developers to write and run tests for their apps.
https://docs.tvlabs.ai/scripting/introduction/getting-starte...
rdtsc
Lua can help if you're handing this over to someone else not just devs who know Elixir.
Also, as the sibling post mentioned, in this case Lua is completely interpreted in an Erlang process. That allows a good amount of sandboxing, they have isolated heaps already and you can control memory limits and other resource usages, and all that in a relatively tiny footprint of a few KBs.
victorbjorklund
This is more for your apps users. Like lets say you have a CRM saas written in Elixir. Then you can allow your users to script things in your app with Lua. If you allow them to use Elixir running in your app you might allow someone to hack your app.
null
dlojudice
Fun fact (probably well-known fact for HN audience): Both Lua and Elixir were created by Brazilians. Lua by Roberto Ierusalimschy and team at PUC-Rio in 1993, and Elixir by José Valim in 2011
rdtsc
davydog187, I just wanted to thank you for stepping up and lending Robert a hand. It's nice to see new releases and lots of cleanups happening in Luerl. The project is a real gem and it's nice to see new activity in it!
davydog187
Thanks, I really appreciate that. While its not my main focus by any means, its been a really fun project to chip away at (both the higher level library and Luerl itself).
I do think that it has the potential to be really great with continued investment
joshprice
This is awesome! Can't wait to find some use cases to embed a sandboxed and safe mini Lua language in our apps.
davydog187
Thanks Josh, hope to see you soon, its been a while
joshprice
Likewise! ElixirConfUS?
davydog187
Probably not, you should come to Code BEAM NYC, although a bit of a trek for you.
I will be trying to travel more in 2026
jkaufmann_
I have been waiting for this my whole life
dpflan
Is this influenced by "Embedding Python in Elixir"?
https://dashbit.co/blog/running-python-in-elixir-its-fine
It certainly is more attractive in implementation. Well done!
davydog187
Both the Lua library and Luerl predate Pythonx. I started this library nearly 2 years ago, its only now that I'm releasing a stable version.
However, Pythonx was originally created by a member of our team, Cocoa, who built it in her own free time. The Livebook team forked her project, conceptually, and released it.
dpflan
Very cool, thank you both for your contributions!
We used Luerl, the underlying Lua engine, in production for years as a sandboxed scripting environment for FarmBot devices back in the day. Users could execute scripts directly on the device to control peripherals. It was a solid library and the community support was great. From an ergonomics perspective, developers preferred this approach over API calls. I am surprised more projects don’t provide a Lua scripting layer.